The wastewater system at CSE, implemented in 2005, has been designed to treat 8000 litres per day based on the assumption that at any given moment at least 100 persons would be ocupying the premises. The treatment modules include a settler, an anaerobic baffled reactor and a planted filter bed. The treated wastewater is stored in an underground sump. This water is used for gardening and landscaping CSE’s premises.

The canteen’s grey water is put through an oil and grease trap to separate matter like oil and scum that floats on the surface of the chamber. After this, the water goes into a settler of 2m x 2m x 2m dimension for primary treatment. This settler is provided with a baffle wall. The settler controls the inflow rate and separates the sludge and scum effectively. The black water from toilets is taken separately into another two chambered settler from where it goes to anaerobic baffled reactor (ABR) for secondary treatment. The ABR has a dimension of 10m x 2m x 1.5 m and consists of a series of chambers (10) in which the wastewater flows up-stream. On the bottom of each chamber activated sludge is retained. Natural biological degradation takes place by forcing the wastewater through active sludge at the bottom of the chamber seperated by baffles. The water is retained in ABR for 24 hours for secondary treatment.

After this, the water from the baffled reactor is mixed with the outlet of the grey water settler. This dilutes the pollutant level of grey water. The combined grey and black water then go into a horizontal planted filter bed for tertiary treatment. It is a rectangular concrete bed of dimensions 22m x 2m x 0.6m and filled with different sized filter materials. It is a hybrid system with plants such as Canna indica and Papyrus planted on the gravel filter for effective removal of nutrients (nitrogen and phosphorus) from the wastewater. The slope of the bed is 1%. The flow direction is mainly horizontal.

The final treated water from the planted filter is stored in the 8000 liters capacity sump. This treated wastewater is pumped out through 1HP automatic pump to meet the horticulture requirements of the building.

Tughlakabad Institutional area has huge water scarcity and ground water table is at the depth of 70m. About 8KL of wastewater is treated and reused. The entire water requirement for horticulture and gardening is met by the treated wastewater.

After six years of complete functioning, the system was put through a process of cleaning (desludging) and repairing. The filter materials were taken out, washed and put back into the system and with replantation on the filter bed. After six months of refunctioning, water quality analysis was done in May 2012. The result showed that the efficiency of the system is 82% in terms of BOD removal. Due to low density of the plants there was not enough nutrient removal from wastewater. The water quality analysis was again done in November 2012, the results of which are shown below.

The per day horticulture requirement of the premises is about 3000 litres. Recycling the wastewater fulfills these requirements.